The present invention relates to a method for operating a D.C. high-speed circuit breaker which can be triggered by overcurrent, particularly for disconnecting a triggered inverter which is connected in parallel with other inverters in a high-voltage D.C. transmission system.
A high-speed circuit breaker of this type is disclosed for example, in the Technische Mitteilungen [Technical News] AEG-TELEFUNKEN 66 (1976), Issue No. 5, at pages 218-219.
In high-voltage D.C. transmission systems containing several inverters connected in parallel, it is necessary to provide over-current protection for the individual inverters when they undergo a commutation failure. According to the prior art, in order to protect such an inverter, it is then necessary to shut down the entire system, until the inverter subject to the malfunction is again working properly or has been disconnected. If the above-mentioned D.C. high-speed circuit breaker is provided in the system, it will disconnect the inverter upon every occurrence of such a malfunction. However, particularly in systems designed with a very small voltage reserve, commutation failures occur even for a very slight drop in the mains voltage. Such failures can easily be overcome within, for example, 20 ms by control measures, such as for example, a so-called "catch circuit", or merely by the influence of a quenching angle adjustment as disclosed in the periodical ETZ-A, Volume 89 (1968), Issue No. 9, at page 218. Even in these cases, however, the D.C. high-speed circuit breaker will interrupt the overcurrent while it is developing and thus terminate it. But this leads to a disconnection in every case of a disturbance, however harmless.